Apparatus for the production of music



B. F. Mxr-:ssNER 1,929,030

APPARATUS FOR THE PRODUCTION OF MUSIL Oct. 3, 1933.

Original Filed Avril 18, 1932 A// hl ANP.

La.l

/2 frn/rams 50 A TTORNEY.

Patented Oct. l 3, 1933 1,929,030 APPARATUS Foa THE rnoDUc'rroN oF MusicBenjamin F. Miessner, Millburn Township, Essex County, N. J., assignorto Miessner Inventions, Inc., a. corporation of New Jersey ApplicationApril 1s, 1932, serial No. 605,961

I Renewed July 8, 1933 15 Claims.

This invention relates -to the production of music from a plurality oftuned vibrators; and

more particularly to instruments wherein the vibration of the vibratorsmay be translated into 5 sound by mechanico-electro-acoustictranslation,

as broadly disclosed and claimed in my co-pending applications, SerialNumber 512,399, filed January 30, 1931, and Serial Number 573,319, fuedNovember 6, 1931.

1oy It is an object of my invention to provide an instrument of theclass described in which the translation of vibrator vibration intosound may be selectively effected either by mechanicoelectro-acoustictranslation or by direct mechanico-acoustic translation, such asemployed for 25 strument of the piano type employingmechanicoelectro-acoustic translation; of particular means for couplingand decoupling the strings to andfrom a resonator; and of improved meansof securing the strings to the bridge.

, 3G lA general object is the provision of an improved instrment of theclass describedi Other and allied objects will morev fully appear fromthe following description and the appended claims.

.f In the detailed description of my invention,

hereinafter set forth, reference is had to the accompanying drawing, ofwhich:-

Figure 1 is a plan view of a portion of an instrument embodying myinvention;

, Figure 2 is a cross-sectional view taken along line 2-2 of Figure 1,in which certain further mechanical, and schematically-shown electrical,-components appear;

Figure 3 is a fractional cross-sectional view 45 similar to a portion ofFigure 2 and illustrating a modification thereof; K

Figure 4 is an enlarged, fractional, crosssectional view of which theright-hand portion is taken along the line 4 4 and the left-hand portionalong vthe line 4'-4' of Figure 1; and

Figure 5,is an enlarged plan view illustrating the detail of thearrangement I have employed for securing the strings to the bridge ofthe instrument shown in Figure 1. In Figure 1, I show aplan view of aportion of an instrument of the piano type, and in Figure 2 across-sectional view thereof taken along linefs2-2 of Figure 1. For thesake of clarity strings, bridgeand hitch-pins, the acoustic insulatingmember 34 of Figure 2, and the sound- 30 board-like member 10 (of Figure2) and its reinforcements, have been omitted from Figure 1; and fromboth these figures have been omitted such conventional elements as frameor plate reinforcing bars, which it will be understood may be employedas customarily. A, In these figures may be seen a rim 1, a rimcross-member 2, and a plurality of rim-beams 3 angularly disposedbetween cross-member 2 and rim 1. All of these parts may be of the con-`70 ventional type and arrangement, except that rim land cross-member 2may extend downwardly below the level of the bottom of rim-beams 3.Spaced above rim-beams 3, and secured to rim 1 and cross-member 2may bea plurality of 75 ribs 4, for example of the type usually employedl forreinforcement of the soundboard of the conventional piano, preferablyarched toward the strings; but no soundboard or 'other resonator isimmediately associated therewith. Secured thereto may be theconventional main or treble bridge 5 and bass bridge 6, over whichbridges the strings 7 are strung to hitch pins 8 in frame or plate 9,which may be of the usual construction. .An improved arrangement forsecuring the strings to the bridge is shown and hereinafter described;but it will be understood that the strings may be secured to the bridgein the usual manner if desired. The usual hammers 19, dampers 20 andhammer action may of course 9 0 be provided for effecting andcontrolling string vibration-i. e., for playing the instrument.

Underneath the rim-beams 3 may be provided a 'soundboard-like member ordiaphragm 10. While this diaphragm may be in general similar to theconventional soundboard, it is preferably thinner and need not be archedtoward the strings. It may be reinforced by a plurality `of ribs 11, butsuch reinforcement is preferably materially less than that of the usualsoundboard, ribs 11 to that end being smaller and more flexible thanconventional ribs, such as 4. Secured to the diaphragm at each of aplurality of points preferably under bridge' 5 is seen a coupling rod12, aiTlxed to the top of which is an armature 13. The coupling rods 12may if desired pass through clearance holes 14 in rim-beams 3.Immediately above each armature 13', and secured to the bottom of bridge5, is provided an electromagnet 15. While only one electromagnet 15 isshown in 110 the armature from the poles of the electromagnets toprevent intermittent contact when bridge 5 vibrates upon playing of theinstrument. To facilitate adjustment the bottom ends of the couplingrods 12 may be provided with a screwdriver slot 21, the/bottom portionsof the rods threaded, and their connection to diaphragm 10 made byscrewing into threaded flanges 22 afiixed to the top of the diaphragm,and to the bottom either of the diaphragm or preferably of one of theribs 11 affixed thereto. By turning of a rod 12 its vertical position,and hence that of the afxed armature 13, may thus be adjusted.

When the electromagnets 15 are energized, upon closing of switch 18, thearmatures will be attracted thereto; and nal adjustment of the verticalposition of the armatures is best made under these conditions, carebeing taken that each armature make intimate contact with both poles ofthe associated electromagnet.

It will be seen that upon the energization of the electromagnets 15 boththe bridge 5 and the diaphragm will be moved, each toward the other. Thebridge 5 is relative immobile, however, because of the resistance todownward motion provided by the arched rib structure 4, which is alreadysustaining a great downward pressure caused by the bearing or" thestrings 7 on the bridge. On the other hand the diaphragm and itsreinforcement, being made relatively flexible, is quite mobile. positionof bridge 5 and diaphragm 1G upon energization of the electromagnetswill be made up almost entirely of motion of the latter and negligiblyof motion of the former; tuning of the strings is thereforeinappreciably affected.

Thus when the electromagnets are energized, the bridge 5 is connected tothe diaphragm, which then acts as a resonator, vibrating in accordancewith the vibration of the bridge, as does the soundboard in aconventional piano. This is of course true for the bass bridge 6, aswell as for the main bridge 5, since the latter necessarily vibrateswith the former because of the support of both by ribs 4. Thus directmechanico-acous- .tic translation of string vibration is eected.

If desired a strip 35, of the same contour as and located directly underbridge 5, may be secured to the top of the diaphragm, providing a mildreinforcement thereof in the direction of the bridge. A fragmentarycross-sectional illustration thereof appears as Figure 3, which isalternative to the similar portion of Figure 2. In Figure 3 the upperthreaded ange 22 has been omitted, the coupling rod being shown threadedinto the strip 35.

When the electromagnets are de-energized, as is the case with switch 13open, the diaphragm is disconnected from the bridge 5 and isconsequently unaffected by string vibration, ceasing tobe a resonator.Under this latter condition the vibration of the strings may betranslated into sound by mechanico-electro-acoustic translation inaccordance with the principles disclosed in the' co-pending applicationsabove referred to. Thus adjacent each string, preferably at a constant,small fractional part of ,its length Hence the combined change ofreaaoeo from the rear end thereof, may be provided a stationaryinsulating member 23 having a conductive surface 24 nearest the strings.The mem ber 23 may be mounted to the plate or frame 9 in any convenientmanner; and the conductive surface 24 is spaced away from each string ingeneral sufficiently to avoid contact therewith under conditions ofmaximum Vibration of the latter.

Conductive surface 24 may be electrically connected to the grid of athermionic vacuum tube 25, whose iilament may be energized as by battery26 and whose anode current may be supplied as from a tap on high voltagebattery or other source 27. The filament of tube 25 may be establishedat a potential higher than that of the negative terminal of battery orsource 27 by the flow of anode current through condensively bypassedresistance 28; and the grid of tube 25 may be biased to the potential ofsuch negative terminal by high resistance 29. Thestrings may beestablished at a D. C. potential different from that of conductivesurface 24 by connection of the plate 9 (with which the strings makeContact) to the positive terminal of battery or source 27. In the Outputcircuit of tube 25 may be provided amplifier 30, and following thelatter may be volume control 31, further amplifier 32,. and loudspeaker33.

.lt will be appreciated that between each string 7 and the conductivesurface 24 a small electrostatic capacityexists, and that thesecapacities in parallel with each other form a total capacity betweenstrings 'and conductive surface. This capacity is charged from batteryor source 27 through resistance 29, and this charge cannot changerapidly because of the high value of the latter resistance. If now anystring 7 be vibrated Jin'a vertical plane, as by striking by its hammeri9, the capacity between it and the conductive surface 24 will be variedoscillator-ily in accordance with the frequency and waveform of thepoint of the string opposite the conductive surface. The total capacitybetween the strings and the surface will be likewise varied, though inreduced degree; and by virtue of the relatively constant charge in thiscapacity the voltage across it will likewise vary. The oscillatoryvariations in this voltage will be seen to be applied to the grid oftube 25; by this tube and succeeding amplier 30 they are amplified; theymay be controlled in respect of amplitude and further ampliied ifdesired by volume control 3l and further amplifier 32, respectively; andnally they may be translated into sound by loudspeaker 33. Thus amechanico-electro-acoustic chain of translation is provided which may beemployed in a degree fully regulated by volume control 31; thistranslation may thus be eifected alternatively to or coincidentally withthe mechanico-acoustic translation effected by member 10 uponenergization of the electromagnets 15.

It is desirable that the tube 25, the conductive Vsurface 23, and partsimmediately associated therewith be protected from stray electrostaticelds. To this end there may be provided about tube 25 and its immediatecircuits electrostatic shielding 36. Similar shielding may be disposedabout the interior of the instrument proper; but I have found it veryconvenient to create an electrostatic shield by painting the inside ofthe rim 1, member 2 and lid 37 with one or more coats of a colloidal,conductive solution-such for example as the graphite preparation soldunder the trade name of Aquadag. The thus painted dynamic type.

Vsectional view of which the right-hand portionis 1,929,oso 3 surfaceshave been indicated in Figure 2 by heavy lines, and the symbol'38 usedto designate the coats of such paint; Electrical contact should be madebetween the shielding and a member having the potential of the plate 9;this is accomplished for rim 1 and cross-member 2 (which are contiguousas seen in Figure l) by the resting of a portion 39 vof the frame on apainted ledge on the inside of rim 1. The painted surface of the lid 37may in turn make electrical contact with the painted portion of rim 1through the hinges customarily provided between lid and rim. To completethe shielding a wire screen 40 may be aixed to the bottom of rim-beams3, its edges making contact with the painted surfaces of rim 1 andcross-member 2.

For use with mechanico-electro-acoustic translation, when this is to beemployed alone or alternatively to mechanico-acoustic translation as'above described, I show an arrangement wherein diaphragm 10 is employedas part of a 'loudspeaker system. This arrangement may be foundadvantageous both in that it provides an efficient loudspeaker and inthat it results in a similar sound source location for each type oftranslation. Thus in Figure 1, I have indicated the contour and typicallocation of two diaphragm-driving translating units 41 of the well-knownelectro- In Figure 4, a fractional crosstaken along line 4 4 and theleft-hand portion along the line 4*--4 of Figure l, I show the detailsof these units'.

Thus in Figure 4 the shell or outer core of each unit 4l may berepresented by 42, the central pole by 43, and the face plate by 44, thelatter forming annular gap 45 with central 'pole 43.

.The shell 42, to which the other parts may be assembled, may befastened to the side of rimbeam 3, and may protrude through an openingprovided therefor in screening 40. Freely positioned in the gap 45" andsecuredgto diaphragm lo may be provided thin' cylinder 47 carryingvoice-coil 48. A iield coil 46 .may be provided vabout central pole 43,such coils being shown .schematically in Figure 4. d battery or otherdirect current source 49 may be provided for energizing the field coils46 ci both the units 4l. 'The voice coils 48 ci the two units 4l may beconnected in series or parallel with each other and to the secondary oftransformer 50, which is provided with primary terminals 5l.

. Reference being had to Figure, 2, 'there will be seen switch 52, bywhich the outputoi amplier 32 lmay be disconnected fromschematicallyshown loudspeaker 33 and connected to terminals 5L If thisis done, there will be supplied to the voice coils 48 the amplifiedoscillations rst translated from `string vibration. By virtue ci theplacement of these coils in the gap 45 and of the high flux thereinmaintained by energized iield coils 46, the oscillations will betranslated into vertical motion of voice coils 4S and hence oi thediaphragm 10, to which they are secured.

The diaphragm, now a part of the loudspeaker system, will be seen to berelatively near the strings '7; and it is necessary to provide acousticinsulation between it and ,the strings to prevent acoustic feed-back.Accordingly I have shown in Figure 2 a sheet 34 of wood, or preferablyof a vibrationallyA dead, composition material, disposed above the rimbeams 3; and between it and the screening 40 carried by the bottom ofthe rim beams may be stuffed soft, sounding-absorbing material 57, suchas felt, whichis indicated in Figures 1 and 4.

While I have shown two translating units 41" driving the diaphragm, itwill be understood that one only may be employed if desired. Aplurality, with eldand voice-coils respectively poled to aid each otherat each instant, is desirable, however, because of the relatively largearea of the diaphragm 4to be vibrated thereby.

In Figure 5, I show a top View of the bridge 5 as engaged by two springs7. It has been shown in the United States Patent No. 1,915,859, issuedJune 27, 1933, to myself and Charles T. Jacobs, that it is of greatconvenience in ne adjustment of the distances of the strings from thetranslating system (in this case conductive surface 23) to pass eachstring in a groove 55 in a screw such as 53, and thence around a simplepin such as 54, both screw and pin being mounted in the bridge. Finedistance adjustment is then readily effected by rotation of the screw. Ihave discovered that two strings may be passed in the same groove onrespectively opposite sides of the screw 53, the strings then crossedand. passed on respectively opposite sides of pin 54. This providessimultaneous distance adjustment of two strings, and is particularlyconvenient when two strings are employed for each note of theinstrument, or of its treble, as may be done in the instrument hereindescribed. z

It will be appreciated that various modifications oi the structures andcombinations of apparatus hereinabove disclosed may be made withoutdeparting from the spirit or scope of my invention as in the appendedclaims dened. Thus the mechanical means (rods l2) coupling the bridge(and through the latter the vibrators) to the resonator l0 may beselectively brought into and out of action in other ways than by theparticularly illustrated electromagnetic control; other forms oimechanicc-electric translating devices may be substituted for theelectrostatic form shown; the switch 18 controlling the energization ofthe electro-magnets may be tandenied with a switch such as 56controlling the electrical amplifying system, one being opened when theother is closed for unicontrolled selective alternation oi translatingsystems, etc.

I claimz'- l. In a musical instrument, the combination or" a pluralityof tuned vibrators; means for vibrating said vibratorsj a diaphragm;mechanical means for coupling said diaphragm with said vibrators; andselectively operable means associated with said coupling means forcontrolling the operation thereof.

2. In a musical instrument, the combination of a plurality of tunedvibrators; means for vibrating said vibrators; a vibratile systemcoupled to all of said vibrators; a diaphragm; mechanical means forcoupling said diaphragm with said vibratile system; and selectivelyoperable means associated with said coupling means for controlling theoperation thereof.

3. In a musical instrument, the combination of a plurality of tunedvibrators; means for .vibrating said vibrators; a mechanico-electrointosound; a diaphragm; a mechanical system for coupling said diaphragm withsaid vibrators;

and means included in said mechanico-electroof a plurality or'tunedvibrators; means for vibrating said vibrators; a vibratile systemcoupled to all of said vibrators; a mechanico-electroacoustic system fortranslating the vibrations ci said vibrators into electric oscillationsand thence into sound; a diaphragm; a mechanical system for couplingsaid diaphragm with said vibratile system; and means included in saidmechanicoelectro-acoustic and said coupling systems for controllingtheir respective operations.

5. ln a musical instrument, the combination ci a plurality of tunedvibrators; means for vibrating said vibrators; a mechanico-electricsystem for translating the vibrations of said vibrators into electricoscillations; a diaphragm; a mechanical system for coupling saiddiaphragm with said vibrators; means for translating said oscillationsinto vibrations of said diaphragm; and means included in saidmechanico-electric and said coupling systems for controlling theirrespective operations.

6. In a musical instrument, the combination of a plurality of tunedvibrators; means for vibrating said vibrators; a diaphragm disposed nearsaid vibrators; mechanico-electric translating apparatus for translatingthe vibrations of said vibrators into electric oscillations; means forvibrating said diaphragm in accordance with said electric oscillations;and acoustic shielding disposed between said diaphragm and saidvibrators.

7. lin a piano, the combination of a plurality of tuned strings; meansfor vibrating said strings;

a vibratile system engaging said strings and comprising at least onebridge and vibratile supporting means therefor; a diaphragm; amechanical coupling system interposed between said vibratile system andsaid diaphragm; and electromagnetic means included in said couplingsystem for controlling the operation thereof.

8. Ina piano, the combination of a plurality o tuned strings; means forvibrating said strings; a vibratile system engaging said strings andcomprising at least one bridge and vibratile supporting means therefor;a diaphragm; and selective means for effecting coupling between saidvibratile system as one member and said diaphragm as the other, saidmeans comprising at least one electromagnet secured to one of saidmembers, at least one armature secured to the other o said members, andmeans operable to energize said electromagnets.

9. In a piano including rigid portions, a plurality of tuned strings andmeans for vibrating said strings, the combination ofv mechanico-elec--tric 'translating apparatus for translating into electric oscillationsthe vibrations of said strings; a diaphragm peripherally secured to saidrigid portions; electro-mechanical translating apparatus operativelyconnected to said diaphragm to vibrate the same; and means for supplyingsaid electric oscillations to said electro-mechanical translatingapparatus.

1G. In a piano including rigidyportions, including a plurality o tunedstrings and including means for vibrating said strings, the combinationof mechanico-electric translating apparatus for translating intoelectric oscillations the Vibrations of said strings; a diaphragmperipherally secured to said rigid portions electro-mechanicaltranslating means operatively connected to said diaphragm to vibrate thesame; and means for supplying said electric oscillations to saidelectromechanical translating means.

l. En a piano including rigid portions, including a plurality of tunedstrings and including means for vibrating said strings,vthe combinationof mechanico-electric translating apparatus for translating intoelectric oscillations the vibrations o said strings; a diaphragmperipherally secured to said rigid portions; at least oneelectro-dynamic oscillation-vibration translating unit, the moving coilof each said unit being connected to a respectively diierent portion ofsaid diaphragm; and means for supplying' said electric oscillations tosaid translating units.

l2. in a musical instrument, the combination of two tuned strings; amember supporting said M strings; a screw rotatable in said member; acircumferential groove in said screw; and a pin in said member near saidscrew, said two strings resting in said groove on opposite sides ofsaid,

screw,V crossing each other between said screw and said pin, and restingagainst respectively opposite sides of said pin.

1 3. in a musical instrument of the type including acase and therein aplurality of vibrators and mecnanico-electric translating apparatus fortranslating the vibrations of said vibrators into electric oscillations,an electrostatic shield for at least a portion of said translatingapparatus, comprising one or more coats of conductive paint applied tosurfaces of said case and an electrically conductive path from saidsurfaces to a point in said translating apparatus.`

14. In a musical instrument of the type including a case and therein aplurality of vibrators and mechanico-electric translating apparatus fortranslating the vibrations of said vibrators into electric oscillations,an electrostatic shield for at least a portion of said translatingapparatus, including one or more coats of conductive paint applied tosurfaces of said case and an electrically conductive path between saidsurfaces and said vibrators. i

l5. l'n a musical instrument, the combination of a mechanicaloscillator; means for producing vibrations thereof, whereby there isproduced therein a vibrating force; means for translating saidvibrations into electric oscillations and said oscillations into asecond vibrating force; a diaphragm; and means selective with respect tosaid two forces and interposed between said oscillator and saiddiaphragm for subjecting said diaphragm to said forces. y

` BENJANUN l?. MIESSNER.

